title: D-amino acids indirectly inhibit biofilm formation in Bacillus subtilis by interfering with protein synthesis.
abstract: The soil bacterium Bacillus subtilis forms biofilms on surfaces and at air-liquid interfaces. It was previously reported that these biofilms disassemble late in their life cycle and that conditioned medium from late-stage biofilms inhibits biofilm formation. Such medium contained a mixture of D-leucine, D-methionine, D-tryptophan, and D-tyrosine and was reported to inhibit biofilm formation via the incorporation of these D-amino acids into the cell wall. Here, we show that L-amino acids were able to specifically reverse the inhibitory effects of their cognate D-amino acids. We also show that D-amino acids inhibited growth and the expression of biofilm matrix genes at concentrations that inhibit biofilm formation. Finally, we report that the strain routinely used to study biofilm formation has a mutation in the gene (dtd) encoding D-tyrosyl-tRNA deacylase, an enzyme that prevents the misincorporation of D-amino acids into protein in B. subtilis. When we repaired the dtd gene, B. subtilis became resistant to the biofilm-inhibitory effects of D-amino acids without losing the ability to incorporate at least one noncanonical D-amino acid, D-tryptophan, into the peptidoglycan peptide side chain. We conclude that the susceptibility of B. subtilis to the biofilm-inhibitory effects of D-amino acids is largely, if not entirely, due to their toxic effects on protein synthesis.
authors.affiliation: Department of Molecular and Cellular Biology, Harvard University, Cambridge, Massachusetts, USA.
authors.forename: Sara A
authors.initials: SA
authors.lastname: Leiman
authors.forename: Janine M
authors.initials: JM
authors.lastname: May
authors.forename: Matthew D
authors.initials: MD
authors.lastname: Lebar
authors.forename: Daniel
authors.initials: D
authors.lastname: Kahne
authors.forename: Roberto
authors.initials: R
authors.lastname: Kolter
authors.forename: Richard
authors.initials: R
authors.lastname: Losick
mesh_terms: D000596:Amino Acids / Q000737:chemistry* / Q000494:pharmacology*; D001412:Bacillus subtilis / Q000235:genetics / Q000378:metabolism / Q000502:physiology*; D001426:Bacterial Proteins / Q000235:genetics / Q000378:metabolism*; D018441:Biofilms / Q000254:growth & development*; D004926:Escherichia coli; D015964:Gene Expression Regulation, Bacterial / Q000187:drug effects*; D013997:Time Factors; D059467:Transcriptome
chemical_list: D000596:Amino Acids; D001426:Bacterial Proteins